7.1 Effects of Soil Conservation Practices
97
To accomplish these goals was envisioned as a guide for planning sustainable land
use and management practices in other areas of the Loess Plateau, China.
7.2 Characteristics of the Nanxiaohegou Catchment
The Nanxiaohegou Catchment (107°37
E, 35°42
N; Fig. 7.1) is a representative
small watershed in the Loess Mesa Ravine Region of the Loess Plateau, with an area
of 36.3 km
2 . Its elevation ranges from 1050 to 1423 m. The catchment is composed
of mesa and gully, and the area ratio of the mesa to the gully is 57:43. A series
of conservation practices have been put into operation in the catchment since the
1950s. The main practices include plantation of trees, establishment of pasturelands,
and construction of terraces and check dams. The terrace is a leveled surface on the
hill to control the slope erosion, while the check dam is built on the gully to retain
hyper-concentration flow from the upper reaches of the catchment. As a huge amount
of soil is deposited in the reservoir of the check dam, the dam farmland is formed,
where crops or trees could be planted.
7.3 Methods and Materials
Rainfall and runoff were monitored at field sites during the treatment period 1954–
2004, except those in 1970, 1986, 1990, 1995–2002. Since 1954, 17 precipitation
observation stations, 8 runoff observation stations, and more than 128 runoff plots
have been continuously built in the Nanxiaohegou Catchment. Figure 7.2 shows
stations and plots currently still in use (Tian et al. 2008). Runoff observation stations
were built at the outlets of the gullies to determine the flow rates of runoff and
sediment. The amount of erosion from the catchment was measured at the Shibamutai
Reservoir runoff observation station near the outlet of the catchment. The inflow and
outflow of the reservoir were observed, and the data during the period 1954–2004
were used to assess the conservation practices. As a contrast, a runoff observation
station was built at the outlet of the Dongzhuanggou Gully where no control practice
was enforced. This gully represents the original state of the catchment before control,
where grazing and farming were free, and the vegetation degree of coverage was near
40% in flood season (XFES 1982). In addition, various runoff plots were established
in the catchment to explore the erosion processes and evaluate the impact factors.
Normal runoff plot was 5 m wide and 16 or 20 m long, while large scale plots
usually covered an area above 77,100 m
2 . The plots were designed on the basis of
various kinds of factors influencing soil and water conservation (Tian et al. 2008).
For the woodland, the factors included the coverage, thickness of the litter layer, and
operating condition of the structure practice, whereas for the grassland, the factors
included the coverage, seed, age, and growth season of the grass. As for the structure
measures, e.g., terrace farmland and check dam farmland, the magnitude of retained
97
To accomplish these goals was envisioned as a guide for planning sustainable land
use and management practices in other areas of the Loess Plateau, China.
7.2 Characteristics of the Nanxiaohegou Catchment
The Nanxiaohegou Catchment (107°37
E, 35°42
N; Fig. 7.1) is a representative
small watershed in the Loess Mesa Ravine Region of the Loess Plateau, with an area
of 36.3 km
2 . Its elevation ranges from 1050 to 1423 m. The catchment is composed
of mesa and gully, and the area ratio of the mesa to the gully is 57:43. A series
of conservation practices have been put into operation in the catchment since the
1950s. The main practices include plantation of trees, establishment of pasturelands,
and construction of terraces and check dams. The terrace is a leveled surface on the
hill to control the slope erosion, while the check dam is built on the gully to retain
hyper-concentration flow from the upper reaches of the catchment. As a huge amount
of soil is deposited in the reservoir of the check dam, the dam farmland is formed,
where crops or trees could be planted.
7.3 Methods and Materials
Rainfall and runoff were monitored at field sites during the treatment period 1954–
2004, except those in 1970, 1986, 1990, 1995–2002. Since 1954, 17 precipitation
observation stations, 8 runoff observation stations, and more than 128 runoff plots
have been continuously built in the Nanxiaohegou Catchment. Figure 7.2 shows
stations and plots currently still in use (Tian et al. 2008). Runoff observation stations
were built at the outlets of the gullies to determine the flow rates of runoff and
sediment. The amount of erosion from the catchment was measured at the Shibamutai
Reservoir runoff observation station near the outlet of the catchment. The inflow and
outflow of the reservoir were observed, and the data during the period 1954–2004
were used to assess the conservation practices. As a contrast, a runoff observation
station was built at the outlet of the Dongzhuanggou Gully where no control practice
was enforced. This gully represents the original state of the catchment before control,
where grazing and farming were free, and the vegetation degree of coverage was near
40% in flood season (XFES 1982). In addition, various runoff plots were established
in the catchment to explore the erosion processes and evaluate the impact factors.
Normal runoff plot was 5 m wide and 16 or 20 m long, while large scale plots
usually covered an area above 77,100 m
2 . The plots were designed on the basis of
various kinds of factors influencing soil and water conservation (Tian et al. 2008).
For the woodland, the factors included the coverage, thickness of the litter layer, and
operating condition of the structure practice, whereas for the grassland, the factors
included the coverage, seed, age, and growth season of the grass. As for the structure
measures, e.g., terrace farmland and check dam farmland, the magnitude of retained